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    <title>Document</title>
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<script>
    // 1.NaN表示不是数值
    console.log(0 / 0)          // NaN
    console.log(-0 / +0)        // NaN

    console.log(5 / 0)            // Infinity
    console.log(5 / -0)           // -Infinity

    /*
            2.NaN的特性
                1.任何涉及到NaN的操作都返回NaN(如NaN/10)
                2.NaN不等于任何值,包括自己(可用 isNaN判断)
     */
    console.log(NaN == NaN)  // false
    console.log(Number.isNaN(NaN)) // true

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